Interference cancellation in microwave backhaul systems

ABSTRACT

A first microwave backhaul assembly comprises a first antenna, a front-end circuit, an inter-backhaul-assembly interface circuit, and an interference cancellation circuit. The first antenna is operable to receive a first microwave signal. The front-end circuit is operable to convert the first microwave signal to a lower-frequency digital signal, wherein the lower-frequency digital signal has energy of a second microwave signal and energy of a third microwave signal. The inter-backhaul-assembly interface circuit is operable to receive information from a second microwave backhaul assembly. The interference cancellation circuit is operable to use the information received via the inter-backhaul-assembly interface circuit during processing of the lower-frequency digital signal to remove, from the first microwave signal, the energy of the third microwave signal. The information received via the inter-backhaul-assembly interface may comprise a signal having energy of the second microwave signal.

CROSS-REFERENCE TO RELATED APPLICATIONS Priority Claim

This application is a continuation of U.S. patent application Ser. No.15/050,537, filed on Feb. 23, 2016, which is a continuation of U.S.patent application Ser. No. 14/586,330, filed on Dec. 30, 2014, now U.S.Pat. No. 9,270,310, which claims the benefit of priority to U.S.provisional patent application 61/921,660, filed on Dec. 30, 2013. Theabove-referenced United States Patent Applications are all incorporatedby reference herein in their entirety.

BACKGROUND

Limitations and disadvantages of conventional approaches to microwavebackhaul systems will become apparent to one of skill in the art,through comparison of such approaches with some aspects of the presentmethod and system set forth in the remainder of this disclosure withreference to the drawings.

BRIEF SUMMARY

Methods and systems are provided for interference cancellation inmicrowave backhaul systems, substantially as illustrated by and/ordescribed in connection with at least one of the figures, as set forthmore completely in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a system comprising two microwave backhaul assemblies forsupporting at least two microwave backhaul links.

FIG. 2 depicts a first example implementation of the microwave backhaulassemblies of FIG. 1.

FIGS. 3A and 3B depict a scenario in which aspects of this disclosureare used for reducing the impact of interference resulting from backlobes of the two microwave backhaul assemblies.

FIG. 4 depicts a second example implementation of a microwave backhaulassembly such as the microwave backhaul assemblies shown in FIG. 1.

FIGS. 5A and 5B depict a scenario in which aspects of this disclosureare used for reducing the impact of interference resulting from sidelobes of the microwave backhaul assembly.

FIG. 6 is a flowchart illustrating an example process for cancellinginterference due to back lobes of two microwave backhaul assemblieslocated at the same site.

FIG. 7 is a flowchart illustrating an example process for cancellinginterference due to side lobes of a microwave backhaul assembly.

DETAILED DESCRIPTION

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory may comprise afirst “circuit” when executing a first one or more lines of code and maycomprise a second “circuit” when executing a second one or more lines ofcode. As utilized herein, “and/or” means any one or more of the items inthe list joined by “and/or”. As an example, “x and/or y” means anyelement of the three-element set {(x), (y), (x, y)}. In other words, “xand/or y” means “one or both of x and y.” As another example, “x, y,and/or z” means any element of the seven-element set {(x), (y), (z), (x,y), (x, z), (y, z), (x, y, z)}. In other words, “x, y, and/or z” means“one or more of x, y, and z.” As utilized herein, the terms “e.g.,” and“for example” set off lists of one or more non-limiting examples,instances, or illustrations. As utilized herein, circuitry is “operable”to perform a function whenever the circuitry comprises the necessaryhardware and code (if any is necessary) to perform the function,regardless of whether performance of the function is disabled or notenabled (e.g., by a user-configurable setting, factory trim, etc.). Asused herein, “microwave” frequencies range from approximately 300 MHz to300 GHz and “millimeter wave” frequencies range from approximately 30GHz to 300 GHz. Thus, the “microwave” band includes the “millimeterwave” band.

FIG. 1 depicts a system comprising two microwave backhaul assemblies forsupporting at least two microwave backhaul links. Shown is a tower 102to which is mounted microwave backhaul assembly 120 a comprising antenna116 a and subassembly 114 a, and a microwave backhaul assembly 120 bcomprising antenna 116 b and subassembly 114 b. In the exampleimplementation shown, the microwave assemblies are used for backhaulinga mobile network (e.g., 3G, 4G LTE, 5G, etc.). Accordingly, also shownare mobile access network antennas 112, remote radio head (RRH) 110, andbasestation 104. The RRH may be connected to the mobile access networkantennas 112 wirelessly or via cables (not shown for clarity ofillustration). One or both of the assemblies 120 a and 120 b may connectto the RRH 110 and/or to the basestation 104 via wires, optical cables,and/or wirelessly (not shown for clarity of illustration). Thebasestation 104 connects to a core network 108 via a backhaul link 106which may be, for example, optical fiber. In other implementations, themicrowave backhaul assemblies 120 a and 120 b may backhaul traffic ofother networks (e.g., television and/or radio distribution networks)instead of, or in addition to, traffic of the mobile network.

An example implementation of the microwave backhaul assemblies 120 a and120 b is described below with reference to FIG. 2.

In operation, each of the microwave backhaul assemblies 120 a and 120 bgenerates one or more desired lobes 124 via which they communicate withrespective link partners (not shown) and one or more undesired lobes118. The microwave backhaul assemblies 120 a communicate with each othervia a link 122 which may be wired, optical, or wireless.

FIG. 2 depicts a first example implementation of the microwave backhaulassemblies of FIG. 1. In FIG. 2, each of the assemblies 120 a and 120 bcomprises its respective antenna 116, an analog/RF front-end circuit210, digital front-end (DFE) circuit 212, interference cancellationcircuit 214, modem circuit 216, and interface 202.

Each of the analog/RF front-end circuits 210 comprises a transmitanalog/RF front-end (AFE), a receive analog/RF front-end (AFE), adigital-to-analog converter (DAC), and an analog-to-digital converter(ADC). The transmit AFE may comprise, for example, one or more filters,an upconverter, and a power amplifier. The receive AFE may comprise, forexample, a low nose amplifier, a downconverter, and one or more filters.The DAC is operable to convert a digital broadband signal (e.g., havinga bandwidth of multiple gigahertz) from the DFE 212 to an analogrepresentation for conveyance to the transmit AFE. The ADC is operableto convert a broadband analog signal (e.g., spanning multiple gigahertz)from the receiver AFE to a digital representation for conveyance to theDFE 212.

For transmit, each of the MODEM circuits 216 is operable to performfunctions such as encoding, interleaving, and bit-to-symbol mapping. Forreceive, each of the MODEM circuits 216 is operable to perform functionssuch as decoding, deinterleaving, and symbol-to-bit demapping forreceive.

Each of the DFE circuits 212 is operable to perform digital processingfunctions such as, for example, amplifier linearization,cross-polarization cancellation, and I/Q offset calibration. Forreceive, the DFE 212 outputs a respective signal 204, which is conveyedto both a respective interference cancellation circuit 214 and arespective interface 202. For transmit, the DFE 212 receives signal 204from a respective interference cancellation circuit 214.

The interface circuit 202 a is operable to output data onto link 122 andthe interface circuit 202 b is operable to receive the data frominterface circuit 202 a and output the data as signal 203 b. Similarly,the interface circuit 202 b is operable to output data onto link 122 andthe interface circuit 202 a is operable to receive the data frominterface circuit 202 b and output the data as signal 203 a. The datacommunicated over the link 122 may comprise, for example: the signal 204a and 204 b, information extracted from the signals 204 a and 204 b,information about the signals 204 a and 204 b (e.g., one or moreperformance metrics such as received signal strength), information abouta configuration of the various circuits of the assemblies 120 a and 120b, data generated by MODEMs 216 a and 216 b, data recovered fromreceived signals by the MODEMS 216 a and 216 b, and/or the like.

The interference cancellation circuit 214 a is operable to processsignals 203 a and 204 a to remove undesired signal components from thesignal 204 a and output the desired signal components of signal 204 a assignal 206 a. Similarly, the interference cancellation circuit 214 b isoperable to process signals 203 b and 204 b to remove undesired signalcomponents from the signal 204 b and output the desired signalcomponents of signal 204 b as signal 206 b. An example is describedbelow with reference to FIGS. 3A and 3B.

FIGS. 3A and 3B depict a scenario in which aspects of this disclosureare used for reducing the impact of interference resulting from backlobes of the two microwave backhaul assemblies. In FIGS. 3A and 3B,assembly 120 a is attempting to receive signal 304 from node 302 a andassembly 120 b is attempting to receive signal 306 from node 302 b. Ingenerating desired radiation lobe 124 a, however, assembly 120 a alsogenerates an undesired back lobe 114 a. Similarly, in generating desiredradiation lobe 124 b, assembly 120 b also generates an undesired backlobe 114 b. Due to the back lobes 118 a and 118 b, energy of signal 306is received by assembly 120 a and energy of signal 304 is received byassembly 120 b. Thus, the two signals interfere with each other. This isshown in FIG. 3B where signals 204 a and 204 b each include componentsof both signals 304 (cross hatched) and 306 (dotted). The amount ofinterference depends on the front-to-back ratios of the antennas 116 aand 116 b. In practice, the amount of interference can be substantialbecause improving the front-to-back ratios beyond a certain point can becost prohibitive. One way to mitigate the effect of this interference isfor signals 304 and 306 to use different frequencies, but such asolution complicates frequency planning and results in inefficient useof spectrum.

In an example implementation, the interface circuits 202 a and 202 bexchange the signals 204 a and 204 b over the link 122. That is,assembly 120 a sends 204 a over the link 122 and assembly 120 b sends204 b over the link 122. In this manner, each of the interferencecancellation circuits 214 a and 214 b is in possession of sufficientinformation for cancelling much of the interference and significantlyimproving the performance of the backhaul system. In the ideal caseshown in FIG. 3B, the interference is perfectly cancelled/removed suchthat signal 206 a contains only a signal 304 component and signal 206 bcontains only a signal 306 component. In a variation of thisimplementation, the interface circuits 202 a and 202 b may exchangeinformation instead of, or in addition to, the signals 204 a and 204 b.For example, the AFEs 210 a and 210 b may measure received signalstrength (RSS) for their respective signals, and the RSS measurementsmay be exchanged between interface circuits 202 a and 202 b over thelink 122. The interference cancellation circuits 214 a and 214 b maythen be configured based on the RSS received from AFEs 210 a and 210 b,respectively. For example, if AFE 210 a measures little or no signal,the system may decide that interference cancellation is unnecessary andtherefore disable interference cancellation circuits 214 a and 214 b toreduce energy consumption.

FIG. 4 depicts a second example implementation of a microwave backhaulassembly such as the microwave backhaul assemblies shown in FIG. 1. Inthe implementation of FIG. 4, the assembly 120 (which may representeither of 120 a and 120 b of FIG. 1) comprises antenna array 402,RF/analog front-end circuit 404, beamforming circuit 406, digitalprocessing circuit 408, interference cancellation circuit 214, and modem216.

The antenna array 402 may comprise, for example, an array of M (aninteger >1) microstrip patches or horns. In an example implementation,the array 402 may be positioned at or near the focal point of a dishsuch as 116 a. For receive, each of the N elements of the array 402 mayoutput a respective one of signals 403 ₁-403 _(M) to AFE 404. Fortransmit, each of the elements of the array 402 may receive a respectiveone of signals 403 ₁-403 _(M) from AFE 404.

The RF/analog front-end circuit 404 comprises, for example, M transmitRF/analog front-ends and M receive RF/analog front-ends, where eachfront end is coupled to a respective one of a plurality of antennaelements of the array 402. Each receive front-end may comprise, forexample, a low-noise amplifier, downconverter, and analog-to-digitalconverter. Each transmit front-end may comprise, for example, adigital-to-analog converter, upconverter, and power amplifier. Forreceive, the AFE 404 may convert N microwave signals 403 to M digitalbaseband signals 405 ₁-405 _(M). For transmit, the AFE 404 may convert Mdigital baseband signals 405 ₁-405 _(M) to M microwave signals 403.

The beamforming circuit 406 is operable to perform digital signalprocessing to implement a beamforming algorithm. For receive, thebeamforming circuit 406 is operable to process M signals 405 ₁-405 _(M)to recover N signals 407 ₁-407 _(N) (each corresponding to a respectivelobe or “beam”), where N is an integer. Such processing may comprisecombining gain and/or phase weighted combining of selected ones of thesignals 405 ₁-405 _(M). For transmit, the beamforming circuit 406 isoperable to process the N signals 421 ₁-421 _(N) to generate signals 405₁-405 _(M) that, when transmitted via the array 402, result in thedesired lobes. Such processing may comprise gain and/or phase weightedcombining of selected ones of the signals 421 ₁-421 _(M).

The DFE 212 is as described above. For receive, the DFE 212 is operableto process each of the signals 401 ₁-407 _(N) to generate acorresponding one of signals 407 ₁-409 _(N). For transmit the DFE 212 isoperable to process each of the signals 417 ₁-417 _(N) to generate acorresponding one of signals 421 ₁-421 _(N).

The ODEM 216 is as described above. For receive, the modem 212 isoperable to recover data from a received signal 404. For transmit, themodem 212 is operable to generate signals 417 ₁-417 _(N), each of whichcorresponds to a signal to be transmitted on a respective lobe.

The interference cancellation circuit 214 is as described above, forexample.

Operation of the example implementation of FIG. 4 is described withreference to FIGS. 5A and 5B.

Referring to FIG. 5A, there is shown the assembly 120 a configured asshown in FIG. 4. Also shown are two nodes 502 a and 502 b. The node 502a is transmitting a signal 504 with radiation pattern 503 a. The node502 b is transmitting a signal 506 with radiation pattern 503 b. Theradiation pattern of the antenna 116 a in FIG. 5A comprises a primarylobe 520 a and a side lobe 520 b. With this arrangement of nodes andradiation patterns, lobe 520 a captures a relatively larger amount ofenergy of signal 504 and relatively lesser amount of energy of signal506. Similarly, lobe 520 b captures a relatively larger amount of energyof signal 506 and relatively lesser amount of energy of signal 504.

For illustration, it is assumed that the assembly 120 desires to receivethe signal 504 from node 502 a. For reception of the signal 504 from thenode 502 a, the beamforming circuit 406 of assembly 120 a is configuredto point the primary lobe 520 a at node 502 a. In the example shown,this comprises placing the primary lobe 502 a “on-boresight.” The lobe502 b is consequently “off-boresight” in FIG. 5A. Because the lobes 520a and 503 b are not perfectly collimated, some energy of signal 506 iscaptured via lobe 520 a. This energy thus amounts to interference. Tomitigate the impact of this interference, the beamforming circuit 406 isconfigured (by control of phase and amplitude coefficients duringcombining of the signals 405 ₁-407 _(M)) to recover a first signal 407 ₁corresponding to energy received via primary lobe 520 a and a secondsignal 407 ₂ corresponding to energy received via the side lobe 520 b.Signal 407 ₁ therefore comprises relatively more energy from the desiredsignal 504 and relatively less energy from the undesired signal 506.Conversely, the signal 407 ₂ comprises relatively more energy from theundesired signal 506 and relatively less energy from the desired signal504. Using the signals 407 ₁ and 407 ₂, the interference cancellationcircuit 214 is operable (e.g., using blind source separation) tocancel/attenuate the undesired signal 506 components such that theamount of energy from signal 506 present in signal 409 ₁ is less thanthe amount of energy from signal 506 present in signal 407 ₁. The modemmay then process signal 409 ₁ to recover the data transmitted on signal504 by node 502 a. FIG. 5B depicts the ideal case in which thecomponents of signal 407 ₁ owing to the undesired signal 506 areperfectly cancelled/removed in the signal 409 ₁. In otherimplementations up to N−2 additional signals 407, corresponding to N−2additional side lobes, may be used for cancelling interference from upto N−2 other sources of interference.

FIG. 6 is a flowchart illustrating an example process for cancellinginterference due to back lobes of two microwave backhaul assemblieslocated at the same site.

In block 602, the assembly 120 a receives the signal 204 a via itsantenna 116 a, front end 210 a, and DFE 212 a. Similarly, the assembly120 b receives the signal 204 b via its antenna 116 b, front-end 210 b,and DFE 212 b.

In block 604, the assembly 120 a outputs signal 204 a onto link 122 viainterface 202 a and the assembly 120 b outputs signal 204 b onto link122 via interface 202 b.

In block 606, the assembly 120 a receives signal 204 b via interface 202a, and outputs it as signal 203 a. Similarly, the assembly 120 breceives signal 204 a via interface 202 b and outputs it as signal 203b.

In block 608, the interference cancellation circuitry 214 a uses thesignals 204 a and 203 a to cancel/attenuate undesired components insignal 204 a and output resulting signal 206 a. Similarly, the circuitry214 b uses the signals 204 b and 203 b to cancel/attenuate undesiredcomponents in signal 204 b and output resulting signal 206 b.

In block 610, the modem 216 a demodulates signal 206 a to recover thedata carried therein. Similarly, the modem 216 b demodulates signal 206b to recover the data carried therein.

FIG. 7 is a flowchart illustrating an example process for cancellinginterference due to side lobes of a microwave backhaul assembly.

In block 702, the assembly 120 receives energy of M signals via theantenna array 402. The captured energy is output as signals 403 ₁-403_(N).

In block 704, the AFE 404 processes the signals 403 ₁-403 _(M) togenerate signals 405 ₁-405 _(M).

In block 706, the signals 405 ₁-405 _(M) are processed by beamformingcircuit 406 to recover signals 407 ₁-407 _(N), each of which correspondsto a respective one of N lobes of a radiation pattern of the antennaarray 402. Each of the signals 407 ₁-407 _(M) contain energy from atleast two signals.

In block 708, the signals 407 ₁-407 _(N) are processed by DFE 212 togenerate corresponding signals 409 ₁-409 _(N).

In block 710, interference cancellation circuitry 214 processes thesignals 409 ₁-409 _(N) to recover one or more of the N signals incidenton the array 402. Each of the signals 409 ₁-409 _(N) comprises energyfrom one or more of N signals received via the antenna array 402.Processing techniques such as blind source separation may thus be usedfor separating out which energy of the signals 409 ₁-409 _(N)corresponds to which of the N signals received via the antenna array402. The situation is analogous to having N equations (the N signals 409₁-409 _(N) representing N lobes) to solve for N unknowns (the N signalsreceived by the antenna 402). The energy of a desired one or more of theN signals is output as one or more signals 404.

In block 712, the modem 216 demodulates the signal(s) 404 to recoverdata carried therein.

In accordance with an example implementation of this disclosure, a firstmicrowave backhaul assembly (e.g., 120 a) comprises a first antenna(e.g., 116 a), a front-end circuit (e.g., 210 a and 212 a), aninter-backhaul-assembly interface circuit (e.g., 202 a), and aninterference cancellation circuit (e.g., 214 a). The first antenna isoperable to receive a first microwave signal (e.g., 209 a). Thefront-end circuit is operable to convert the first microwave signal to alower-frequency digital signal (e.g., 204 a), wherein thelower-frequency digital signal has energy of a second microwave signal(304) and energy of a third microwave signal (306). The second microwavesignal may be destined for the first microwave backhaul assembly. Thethird microwave signal may be destined for the second microwave backhaulassembly. The inter-backhaul-assembly interface circuit is operable toreceive information from a second microwave backhaul assembly (e.g., 120b). The interference cancellation circuit is operable to use theinformation received via the inter-backhaul-assembly interface circuitduring processing of the lower-frequency digital signal to remove, fromthe first microwave signal, the energy of the third microwave signal.The information received via the inter-backhaul-assembly interface maycomprise a signal (e.g., 204 b) having energy of the second microwavesignal. The information received via the inter-backhaul-assemblyinterface may comprise a signal (e.g., 203 b) having energy of the thirdmicrowave signal. The information received via theinter-backhaul-assembly interface may comprise an indication of anamount of energy of the third microwave signal received by the secondmicrowave backhaul assembly. The first antenna and a second antenna(e.g., 116 b) of the second microwave backhaul assembly may be adjacentto one another such that one or more radiation lobes of the firstantenna (e.g., 124 a) overlap with one or more radiation lobes of thesecond antenna (e.g., 118 b). The first antenna and a second antenna ofthe second microwave backhaul assembly may be mounted to the samesupport structure (e.g., tower 102). The antenna may comprise a firstparabolic reflector. The second antenna may comprise a second parabolicreflector. The first parabolic reflector and the second parabolicreflector may be mounted facing away from each other on a supportstructure. The front-end circuit may be operable to measure aperformance metric for the first microwave signal. Theinter-backhaul-assembly interface circuit may be operable to output themeasured performance metric to a destination external to the firstmicrowave backhaul assembly (e.g., to the second microwave backhaulassembly).

The present method and/or system may be realized in hardware, software,or a combination of hardware and software. The present methods and/orsystems may be realized in a centralized fashion in at least onecomputing system, or in a distributed fashion where different elementsare spread across several interconnected computing systems. Any kind ofcomputing system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computing system with a program orother code that, when being loaded and executed, controls the computingsystem such that it carries out the methods described herein. Anothertypical implementation may comprise an application specific integratedcircuit or chip. Some implementations may comprise a non-transitorymachine-readable (e.g., computer readable) medium (e.g., FLASH drive,optical disk, magnetic storage disk, or the like) having stored thereonone or more lines of code executable by a machine, thereby causing themachine to perform processes as described herein.

While the present method and/or system has been described with referenceto certain implementations, it will be understood by those skilled inthe art that various changes may be made and equivalents may besubstituted without departing from the scope of the present methodand/or system. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the presentdisclosure without departing from its scope. Therefore, it is intendedthat the present method and/or system not be limited to the particularimplementations disclosed, but that the present method and/or systemwill include all implementations falling within the scope of theappended claims.

What is claimed is:
 1. A system comprising: a first receiver operable tooutput a digital signal comprising a desired signal with interference;an interface operable to receive information from a second receiver,wherein the information received via the interface comprises a signalhaving energy at the frequency of the desired signal; and aninterference cancellation circuit operable to use the informationreceived via the interface to reduce the interference.
 2. The system ofclaim 1, wherein the information received via the interface comprises asignal having energy at the frequency of the interference.
 3. The systemof claim 1, wherein the information received via the interface comprisesan indication of an amount of energy of the interference received by thesecond receiver.
 4. The system of claim 1, wherein: the desired signalis destined for the first receiver; and the interference is related to asignal destined for the second receiver.
 5. The system of claim 1,wherein one or more radiation lobes of a first antenna, operably coupledto the first receiver, overlap with one or more radiation lobes of asecond antenna, operably coupled to the second receiver.
 6. The systemof claim 5, wherein the first antenna and the second antenna are mountedto the same support structure.
 7. The system of claim 5, wherein: thefirst antenna comprises a first parabolic reflector; the second antennacomprises a second parabolic reflector; and the first parabolicreflector and the second parabolic reflector are mounted facing awayfrom each other on a support structure.
 8. The system of claim 1,wherein the interface is operable to output the digital signal to adestination external to the first receiver.
 9. The system of claim 1,wherein: the first receiver is operable to measure a performance metricfor a received microwave signal; and the interface is operable to outputthe measured performance metric to a destination external to the firstreceiver.
 10. A method comprising: receiving, via a first antenna of afirst receiver, a first microwave signal; converting, via the firstreceiver, the first microwave signal to a lower-frequency digitalsignal, wherein the lower-frequency digital signal comprises a desiredsignal and interference; receiving, via an interface, information from asecond receiver; and processing, by an interference cancellation circuitusing the information received via the interface, the lower-frequencydigital signal to reduce the interference.
 11. The method of claim 10,wherein the information received via the interface comprises a signalhaving energy at the frequency of the desired signal.
 12. The method ofclaim 10, wherein the information received via the interface comprises asignal having energy at the frequency of the interference.
 13. Themethod of claim 10, wherein the information received via the interfacecomprises an indication of an amount of energy of the interferencereceived by the second receiver.
 14. The method of claim 10, wherein:the desired signal is destined for the first receiver; and theinterference is related to a signal destined for the second receiver.15. The method of claim 10, wherein one or more radiation lobes of afirst antenna, operably coupled to the first receiver, overlap with oneor more radiation lobes of a second antenna, operably coupled to thesecond receiver.
 16. The method of claim 15, wherein the first antennaand the second antenna are mounted to the same support structure. 17.The method of claim 15, wherein: the first antenna comprises a firstparabolic reflector; the second antenna comprises a second parabolicreflector; and the first parabolic reflector and the second parabolicreflector are mounted facing away from each other on a supportstructure.
 18. The method of claim 10, comprising outputting, by theinterface, the lower-frequency digital signal to a destination externalto the first receiver.
 19. The method of claim 1, comprising: measuring,by the first receiver, a performance metric for the first microwavesignal; and outputting, by the interface, the measured performancemetric to a destination external to the first receiver.
 20. A systemcomprising: a first receiver operable to output a digital signalcomprising a desired signal with interference; an interface operable toreceive information from a second receiver, wherein the informationreceived via the interface comprises a signal having energy at thefrequency of the interference; and an interference cancellation circuitoperable to use the information received via the interface to reduce theinterference.
 21. The system of claim 20, wherein the informationreceived via the interface comprises a signal having energy at thefrequency of the desired signal.
 22. The system of claim 20, wherein theinformation received via the interface comprises an indication of anamount of energy of the interference received by the second receiver.23. The system of claim 20, wherein: the desired signal is destined forthe first receiver; and the interference is related to a signal destinedfor the second receiver.
 24. The system of claim 20, wherein one or moreradiation lobes of a first antenna, operably coupled to the firstreceiver, overlap with one or more radiation lobes of a second antenna,operably coupled to the second receiver.
 25. The system of claim 24,wherein the first antenna and the second antenna are mounted to the samesupport structure.
 26. The system of claim 24, wherein: the firstantenna comprises a first parabolic reflector; the second antennacomprises a second parabolic reflector; and the first parabolicreflector and the second parabolic reflector are mounted facing awayfrom each other on a support structure.
 27. The system of claim 20,wherein the interface is operable to output the digital signal to adestination external to the first receiver.
 28. The system of claim 20,wherein: the first receiver is operable to measure a performance metricfor a received microwave signal; and the interface is operable to outputthe measured performance metric to a destination external to the firstreceiver.